Okla. Stat. tit. 74 § 913a
Any employee who was denied membership in the Oklahoma Public Employees Retirement System or was forced to discontinue participation in the System as a result of receiving a retirement benefit from another retirement plan authorized under any other law of this state may receive credit for those years of service accumulated by the employee during the time the employee was denied participation. To receive this service credit, the member shall pay to the Board prior to January 1, 1991, for each year of service purchased pursuant to this subsection, a ten percent (10%) contribution and interest of ten percent (10%), provided however, effective January 1, 1991, to receive the service credit, the member shall pay the amount determined by the Board pursuant to Section 39 of this act. Any person purchasing service credit pursuant to this subsection shall not be eligible for prior or participating service credit if the member is receiving or eligible to receive service credit for such time in any other state retirement plan.
Okla. Stat. tit. 74, § 913a